If you are an organized sort of person who likes to remember what the hell you were trying to do when you ran a particular simulation you might find it useful to put comments in your input file. In PLUMED you can do this as comments can be added using a # sign. On any given line everything after the # sign is ignored so erm... yes add lines of comments or trailing comments to your hearts content as shown below (using Shakespeare is optional):

Click on the labels of the actions for more information on what each action computes
tested on v2.7
# This is the distance between two atoms:
the pair of atom that we are calculating the distance between.
=1,2 Snout: UPPER_WALLS
the input for this action is the scalar output from one or more other actions.
compulsory keyword the positions of the wall.
compulsory keyword the force constant for the wall.
=3.0 # In this same interlude it doth befall. # That I, one Snout by name, present a wall.


An alternative to including comments in this way is to use the command ENDPLUMED. Everything in the PLUMED input after this keyword will be ignored.